Curable polyepoxide compositions

ABSTRACT

This application relates to curable compositions, based on cycloaliphatic epoxides in admixture with epoxy hardeners and polymers of butadiene, which can be cast into articles of desired configuration or used as binders in the preparation of laminates, and cured at elevated temperatures to form articles characterized by excellent physical properties such as tensile strength, toughness, resistivity to development and propagation of internal cracks, heat distortion temperatures and also characterized by excellent electrical properties.

United States Patent Soldatos et a1. 45 Aug, 22, 1972 r 1 1 CURABLEPOLYEPOXIDE 3,219,515 11/1965 Rice ..260/837 COMPOSITIONS 3,312,7544/1967 Marks ..260/837 72 Inventors: Anthony c. Soldatos, Kendall Park;giggggg 3 132; y i g "52 3 Allison S. Burhanswest Minington, 1e 0/ 36both of NJ. OTHER PUBLICATIONS [73] ASSigneeI Union Carbide Corporation,Ne McGarry, Frederick J. et al., Toughening of Glassy York, CrosslinkedPolymers With Elastomeric Inclusions Ike. l, [21] Appl. No.: 886,781Primary Examiner-Paul Lieberman Att0rneyPaul A. Rose, Aldo J. Cozzi andJames C. 52 US. Cl ..260/836, 117/124 E, 117/126 GE, Mamas117/126GR,1l7/132BE,ll7/132CB, TRQ 117/138.8 BE, l17/138.8 CB, 117/155UA, [571 ABS CT 1 4 1 135 1 1 2 0 323 p This application relates tocurable compositions, 2 0 37 p 2 0 7 4 p 2 0 31 based on cycloaliphaticepoxides in admixture with 51 Int. (:1. ..C08g 45/04 p y hardeners and py of butadiene, which [58] Field of Search ..260/836, 837 can be castinto micles of desired configuration or used as binders in thepreparation of laminates, and [56] References Cited cured at elevatedtemperatures to form articles characterized by excellent physicalproperties such as UNITED STATES- PATENTS tensile strength, toughness,resistivity to development and propagation of internal cracks, heatdistortion SIC-be". e pe u e and also characterized excellent elec2,947,338 8/1960 Reid ..260/836 meal properties 3,100,160 8/1963 Korpman..260/836 3,135,716 6/1964 Uraneck ..260/836 19 Claims, No DrawingsCURABLE POLYEPOXIDE COMPOSITIONS This invention relates to curablecompositions based on cycloaliphatic epoxides in admixture with epoxyhardeners and polymers of butadiene; and cured products obtainedtherefrom. More particularly, this invention relates to curablecompositions, as defined above, which can be cast into articles ofdesired configuration or used as binders in the preparation oflaminates, and cured at elevated temperatures to form articlescharacterized by excellent physical properties such as tensile strength,toughness, resistivity to development and propagation of internalcracks, heat distortion temperatures and also characterized by excellentelectrical properties. The compositions of this invention by virtue ofthe excellent properties find wide use as the matrix material or binderin the production of fiber reinforced laminates useful in suchapplications as printed electrical circuits, structural laminates andthe like.

Curablerzompositions, as for example, curable compositions based onpolyglycidyl ethers of polyhydric phenols, have found utility ascompositions which can be cast into shaped articles of desiredconfiguration and as compositions which can be used as the matrixmaterial in the production of fiber reinforced laminates. It has beenfound, however, that articles and laminates produced from thesecompositions are subject to internal cracking when subjected to adynamic load. In many instances the cracks propagate, and in time, thereis a complete failure of the shaped article or of the laminate.

As a result of the intemal cracking problem, various modifiers have beensuggested as additives to compositions based on polyglycidyl ethers forthe purpose of eliminating or suppressing the development andpropagation of internal cracking. The addition of various modifiers topolyglycidyl ether compositions has not proved to be particularlydesirable, however, as these modifiers tend to degrade other propertiesof these compositions, as for example, the tensile strength thereof.

The present invention provides curable epoxy compositions, based oncycloaliphatic epoxides in admixture with epoxy hardeners and polymersof butadiene, having excellent physical and electrical properties aspreviously described.

Suitable cycloaliphatic epoxides for purposes of this invention arethose having an average of more than one vicinal epoxy group permolecule. The epoxy groups can be terminal epoxy groups or internalepoxy groups as exemplified by the cycloaliphatic epoxides which aresubsequently described. Particularly desirable cycloaliphatic epoxidesare the cyclohexane diepoxides, that is epoxides having at least onecyclohexane ring to which is attached at least one vicinal epoxy group.

Illustrative of suitable cycloaliphatic epoxides are the following:

FORMULA I Diepoxides of cycloaliphatic esters of dicarboxylic acidshaving the formula;

wine-mommy wherein R through R,,, which can be the same or different arehydrogen or alkyl radicals generally containing one to nine carbon atomsinclusive and preferably containing one to three carbon atoms inclusiveas for example methyl, ethyl, n-propyl, n-butyl, n-hexyl, 2- ethylhexyl,n-octyl, n-nonyl and the like; R is a valence bond or a divalenthydrocarbon radical generally containing one to nine carbon atomsinclusive and preferably containing four to six carbon atoms inclusive,as for example, alkylene radicals, such as trimethylene, tetramethylene,pentamethylene, hexamethylene, 2-ethylhexamethylene, octamethylene,nonamethylene, and the like; cycloaliphatic radicals, such asl,4cyclohexane, 1,3-cyclohexane, 1,2

cyclohexane, and the like.

FORMULA n A 3,4-epoxycyclohexylmethyl 3,4epoxycyclohexane carboxylatehaving the formula:

wherein R through R which can be the same or different are as definedfor R in Formula I. Particularly desirable compounds are those wherein Rthrough R are hydrogen.

Among specific compounds falling within the scope of Formula II are thefollowing: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,3,4-epoxyl-methylcyclohexylmethyl3,4-epoxy-l-methylcyclohexanecarboxylate,6-methyl-3,4-epoxycyclohexylmethyl6-methyl-3,4-epoxycyclohexanecarboxylate,3,4-epoxy-3-methylcyclohexylmethyl 3,4-epoxy-3-methylcyclohexanecarboxylate, 3,4-epoxy-5-methylcyclohexylmethyl3,4-epoxy-S-methylcyclohexanecarboxylate. Other suitable compounds aredescribed in US. Pat. No. 2,890,194 to B. Phillips et al.

FORMULA Ill Diepoxides having the formula:

and the like The hardeners which are suitable for purposes of thisinvention are compounds which undergo a reaction with the cycloaliphaticepoxides, as opposed to compounds which catalyze the self-reaction ofthe cycloaliphatic epoxides.

Among suitable hardeners which are admixed with the cycloaliphaticepoxides and polymers of butadiene to provide the curable compositionsof this invention are the following:

1. phenolic hardeners having at least 2 phenolic hydroxyl groups andpreferably having. at least 3 phenolic hydroxyl groups per molecule.

2. polybasic acids having at least 2 carboxylic acid groups permolecule.

3. anhydrides of acids having at least 2 carboxylic I acid groups permolecule.

Exemplary of suitable phenolic hardeners are the following polyhydricphenols: catechol, hydroquinone, hydroxyhydroquinone, phloroglucinol,resorcinol and pyrogallol; the di and polynuclear phenols such as thebisphenols described in Bender et al., U.S. Pat. No. 2,506,486 andpolyphenylols such as novolac condensates of a phenol and a saturated orunsaturated a1- dehyde containing an average of from three to 20 or morephenylol groups per molecule (cf. book by T. S.

Carswell entitled Phenoplasts, published in 1947 by- IntersciencePublishers of New York).

Examples of suitable polyphenylols derived from a phenol and anunsaturated aldehyde such as acrolein are the triphenylols,pentaphenylols and heptaphenylols described in U.S. Pat. No. 2,885,385to A. G. Famham, issued May 5, 1959.

The phenols may contain alkyl or aryl ring substituents or halogens, asexemplified by the alkyl resorcinols, the tribromo resorcinol and thediphenols containing alkyl and halogen substituents on the aromatic ring(Bender et al., U.S. Pat. No. 2,506,486).

The polyhydric phenols can consist of two or more phenols connected bysuch groups as methylene, a1- kylene, ether, ketone, or sulfone. Theconnecting groups are further exemplified by the following compounds:bis(p-hydroxyphenyl)ether, bis(p-hydroxyphenyl)ketone,bis(p-hydroxyphenyl)methane, bis(phydroxyphenyl )dimethyl methane, bis(p-hydroxyphenyl)sulfone and the like.

For purposes of stoichiometric calculations with respect to phenolichardeners, one phenolic hydroxyl group is deemed to react with one epoxygroup.

Illustrative of suitable polybasic acids are the polycarboxylic acids ofthe formula:

FORMULA IV HOOC(CH ),-COOH wherein f is an integer generally having avalue of from 1 to inclusive, as for example, malonic, succinic,glutaric,-adipic, pimelic, suberic, azelaic, sebacic and the like. Otherexamples of suitable acids are phthalic acid, isophthalic acid,terephthalic acid and the like. Further acids are enumerated in U.S.Pat. No. 2,918,444 to B. Phillips et al., issued Dec. 22, 1959.

Among other suitable polybasic acids, having at least two carboxylicgroups per molecule, can be noted the following: tricarballylic acid,trimellitic acid and the like. Other such suitable polybasic acids,including .polyesters thereof, are described in U.S.v Pat. No.

2,921,925 to B. Phillips et al.

Suitable anhydrides are the anhydrides of the acids listed above.

For purposes of stoichiometric calculations with respect to acids, onecarboxyl group is deemed to react with one epoxy group; with respect toanhydrides, one anhydride group is deemed to react with one epoxy group.

Among other suitable hardeners are those such as dicyandiarnide and thelike.

Polymers of butadiene which are admixed with the cycloaliphatic epoxidesand hardeners therefor to provide the compositions of this invention arecarboxyl and mercapto containing poly(butadiene) and copolymers ofbutadiene and acrylonitrile wherein: the homopolymers and copolymershave a molecular weight of about 500 to about 15,000, preferably about1,000 to about 10,000 and have an average of more than one terminalcarboxyl or terminal mercapto group per molecule. As a general rule, thecopolymers contain about 1 to about 99 percent by weight and preferablyabout 5 to about 50 percent by weight combined acrylonitrile.

Carboxyl and mercapto terminated polymers of butadiene as defined arefurther described in U.S. Pat. No. 3,135,716 to Carl A. Uraneck et al.,patented June 2, 1964, U.S. Pat. No. 3,117,190 to Henry L. Hsieh,patented Apr. 6, 1965, and in U.S. Pat. No. 3,285,949 to A. R. Siebert,patented Nov. 15, 1966.

In formulating the compositions of this invention, the hardener, epoxideand polymer of butadiene are simply admixed at room temperature in asuitable container. As a rule the hardener is generally used in amountsof about 40 percent of stoichiometric to about 60- percent in excess ofstoichiometric. It is preferred to use about percent of stoichiometricto about stoichiometric amounts.

The polymer of butadiene is used in amounts of about 5 to about 250parts by weight and preferably about 10 to about 100 parts by weightbased on 100 parts by weight of the epoxide.

It is to be understood that other additives can be added to thecompositions of this invention as is well known in the epoxy art. Amongsuch additives are pig ments such as carbon black and the like,accelerators such as ethylene glycol, tertiary amines and the like,fillers such a as clay, silica and the like.

compositions will, of course, vary and depend, in part,

The temperature to which the compositions of this CH O C invention areheated in order to effect a cure of the g \0 referees;

' mixing the materials in a glass container at room tem- 40 upon theexact formulation of the compositions. As a r rule, this temperature isin the range of about 100C. to about 200 C. for a period of time rangingfrom about 1 t06h0urst or V. As stated, the compositions of thisinvention can be formed into castings and used in applications whereinThe carboxyl-terminated polymer of this example This copolymer had thefollowing properties:

epoxy resins are generally utilized, for example, as elec- F1351: m'cale assn etinsm ti an t i se-.-- m prermpnalyqarbgxyl In addition, thecompositions of this invention find I iifif'cililtel u 31 220 wideutility as binders in the preparation of laminates g 'ggi'i :fg'gi l9 4and filament-wound structures. In producing a com, Q'iscosity in 27 c.,position suitable for this purpose, the composition if ggg fi 120.000necessary is dissolved in any suitable organic solvent to 2 25 y 0.948form a solution having a solids content of about 30 to about 70 percentby weight. As a rule, the organic sol- The Gardner Impact Test wasconducted by striking vent used is a ketone, such as methylethyl ketone,cured specimens 0.1 inch thick by 2.0 inches in diisopropyl ketone andthe like. This solution is'then diameter unless otherwise noted with a4-pound was a copolymer of acrylonitrile and butadiene-l,3.

used to impregnate, by any suitable method, for examround-nose rod. Theenergy required to fracture the ple, dipping, spraying and the like anydesired material, specimen is expressed in inch-lbs.

for instance, glass cloth, glass filaments, carbon cloth, The boilingwater test was conducted by immersing carbon filaments, nylon filaments,metal fibers, paper cured weighed specimens inch in diameter in and thelike. The impregnated material is then formed b g Water for 24 hourswiping he specimens into a desired shape and the composition cured toits afief the 24-hour P r o C ing r m emperature and noting the changein weight if any.

The disclosure of all references noted in the applica- 0 LE 2 tion, p tets nd otherwise are incorporated h i b This example illustrates theexcellent bonding strength of the compositions of this invention.

The following examples further illustrate thfi present below wereprepared as in Example 1 and lnvention and are not intended to limit thescope 3 5 used, i h case, to b d together two pieces f 1 ,tlls se iaemanner- In the examples which follow, amounts are in parts by weight andthe compositions were prepared by adin ASTM Test D'l00264 Compositions,the formulations of which are noted minum specimens, the Lap ShearStrength of which was determined according to the procedure describedCompositions Perature- Y Control 2 H EXAMPLE 1 Polyepoxide 100 100Compositions, the formulations of which are noted (Same as in Examp 1below, were prepared by admixing the components in a ggffiggg 100 glassflask at room temperature and subjected to the Ethylene glycol 1.0 1.0tests, also noted below, after being cured to infusible L products bybeing subjected to the following cure cy- (Same as in Example 1) 1 LapShea; Sgength, psi 2 6 5 z 3 1 99 2 2 hours at a temperature C. 50 2;30F, 113 i943 4 hours at atemperature C. a! 1279 1780 CompositionsControl 1 A B C D E F G Polyepoxide Hexahydrophthalic acid anhydrideTensile strength, ASIM D-638-64T, p.s.i Elongation, percent AS'IMD-638-64'1 1. 24-hour water boil, percent increase in weight 0. 94 0. 940. 96 0. 99

Specimen was 0.6 inch thick.

X MPLE} The polyepoxide of this example was 3,4-epoxycyclohexylmethyl3,4-epoxycyclohexane carboxylate I Compositions, the formulations ofwhich are noted having the formula: below, were prepared as described inExample 1 and being subjected to the following cure cycle:

l subjected to the test which is also noted below after 2 hours at atemperature of 120 C. 4 hours at a temperature of 160 C.

, Compositions Control 3 l J Polyepoxide 100 100 100 100 (Same as inExample 1) Hexahydrophthalic acid 100 100 100 100 anhydride Ethyleneglycol 1.5 1.5 1.5 1.5 N,N-Dimethylbenzylamine 1.0 1.0 1.0 1.0Carboxyl-terminated polymer (Same as in Example 1) 10 20Carboxyl-terminated po1y-(butadiene-1,3) 10 Heat distortion temperaturein 'C. 191 187 188 188 The homopolymer had the f ollowing properties:Carboxyl content, percent by weight 3.0 Terminal carboxyl functionality1.90 Molecular weight 3000 Specific gravity 25C/25C 0.90

- EXAIvIPLE 4 The composition, the formulation of which is noted below,was prepared as described in Example 1 and subjected to the tests notedbelow after being cured to an infusible product by being subjected tothe following cure cycle:

2 hours at a temperature of 120 C.

4 hours at a temperature of 160 C.

Composition L Polyepoxide 100 (Same as in Example 1) Hexahydrophthalicacid 100 anhydride Ethylene glycol 1.5 N,N-dimethylbenzylamine 1.0Mercapto-terminated polymer 5 Tensile Strength, psi 9,600 ASTM D-638-64TElongation, percent 3 The mercapto-terminated copolymer of this examplewas a copolymer of butadiene-1,3 and acrylonitrile, terminated withmercapto groups. This copolymer had the following properties:

Mercapto content,

percent by weight 3.10

Terminal mercapto functionality 1.6

Molecular weight 700 Combined acrylonitrile percent by weight 24 vSpecific gravity 2SC/25C 0.98

EXAMPLE 5 The composition, the formulation of which is noted below, wasprepared as described in Example 1 and subjected to the tests notedbelow after being cured to an infusible product by being subjected tothe following cure cycle:

2 hours at a temperature of 120 C.

4 hours at a temperature of 160 C.

Composition Polyepoxide (Same as in Example 1) Hexahydrophthalic acid100 anhydride Ethylene glycol 1.5 N,N-Dirnethylbenzylamine 1.0Carboxyl-terminated polybutadiene 10 (Same as in Example 3) Gardnerimpact inch-Lbs. 70

- EXAMPLE 6 This example illustrates the excellent electrical propertiesof the compositions of this invention.

Tests were conducted on the compositions noted in Example 1.

In this example carboxyl-terminated copolymers of butadiene andacrylonitrile of various molecular weights were used to formulatecompositions of this inyqmim. -7 .4

Compositions, the formulations of which are noted below, were preparedas described in Example 1 and subjected to the tests, also noted belowafter being subjegted to the followingeure cyclez 2 hours at atemperature of C. 4 hours at a temperature of C.

Compositions M Polyepoxide 100 100 (Same as in Example 1)hexahydrophthalic acid anhydride Ethylene glycol N,N-DimethylbenzylamineCarboxyl-terminated copolymer of butadiene-1,3 andacrylonitrilemolecular weight 5800 Combined acrylonitrile I 19.5 percentby weight terminal Carboxyl functionality 1.7 Carboxyl-ten'ninatedcopolymer of butadiene-l ,3 and acrylonitrilemolecular weight 10,000Combined acrylonitrile 19 percent by weight terminal carboxylfunctionality 1.78 Tensile Strength, ASTM D-638-64T, psi

Elongation, percent,

ASTM D-638-64T Gardner impact Inch. Lbs.

9 EXAMPLE 7 This example shows that laminates prepared using thecompositions of this invention as the matrix or binder material haveexcellent retention of strength under dynamicfatigue stressing.

Laminates were prepared using Control 1 and Composition A of Example 1.

Each composition was used as a laminating varnish by impregnating 181weave glass cloth therewith, stacking 12 plies of impregnated cloth, oneupon the other and subjecting the stacked plies to the following curecycle:

1 hour at 120 C. under a pressure of 200 psi 1 hour at 160 C. under apressure of 200 psi 5 hours at 160 C. under a pressure of 200 psi Thelaminates were then tested under tensile stress using a Sonntag 1800 cpmFatigue Testing Machine, Model SF-lU.

At a 15,000 psi stress level the laminate based on Control 1 failed at178,000 cycles.

At a 15,000 psi stress level the laminate based on Composition Adid notfail until 490,000 cycles.

EXAMPLE 8 the curve.

The compositions tested are those of Example 1 and are noted below:

Area Under Tensile Elong- Composition Strength ation Curve Control 17,500 1.9 86 in.lb./in. Composition A 12,000 5 382 in.lb./in.='Composition B 10,600 5.3 370 in.lb./in. Composition C 9,390 8 458in.lb./in.

The following epoxides were used in formulating compositions identicalto those of Compositions A-D of Example 1 (with the exception of theepoxide) with similar results as to properties.

10 In order to further show the unique properties of the compositions ofthis invention, two compositions, Control 4 and Control 5, theformulations of which are noted below, were prepared in a manner asdescribed 5 for Example 1, subjected to a cure cycle and tested. Curecycle, tests ad results of the tests are noted below.

Cure cycle: 1.5 hours at 80 C. 1 hour at 90 C. 2 hours at 120 C. 4 hoursat 160 C.

Compositions Control 4 Control 5 A--D of Example 1 (with the exceptionof the an-- ,hxdfibatene c r r e t a to Pr p e 1. phenol-formaldehydenovolac having about four phenolic hydroxyl groups per molecule 2 Plthdk a hat s a me l. A curable composition comprising a cycloaliphaticpolyepoxide, a phenolic hardener, an acid hardener or an acid anhydridehardener therefore in an amount of about percent of stoichiometric toabout 60 percent in excess of stoichiometric and a polymer of butadienewhich is a carboxyl containing poly(butadiene) or a copolymer ofbutadiene and 40 acrylonitrile, said poly(butadiene) and copolymerhaving only terminal carboxyl groups in an average of more than oneterminal carboxyl per molecule and being present in said composition inan amount of about 5 to about 250 parts by weight per 100 parts by wa flis s P d 2. A. curable composition as defined in claim 1 wherein thecycloaliphatic epoxide is a cyclohexane .q e e- 3. A curable compositionas defined in claim 1 wherein thecycloaliphatic epoxide has the formula:

4. A curable composition as defined in claim 3 wherein R through arehydrogen and R is (Cl-1 5. A curable composition as defined in claim -1wherein the cycloaliphatic epoxide has the formula:

wherein R through R are as defined for R, of claim 3.

6. A curable composition as defined in claim 5 wherein R through R arehydrogen.

7. A curable composition as defined in claim 1 wherein the hardener is aphenolic epoxy hardener having at least two phenolic hydroxyl groups permolecule.

8. A curable composition as defined in claim 1 wherein the hardener is apolybasic acid having at least two carboxylic acid groups per molecule.

9. A curable composition as defined in claim 1 wherein the hardener isan anhydride of a polybasic acid.

10. A curable composition as defined in claim 9 wherein the anhydride ishexahydrophthalic acid anhydride.

11. A curable composition as defined in claim 1 wherein the butadienepolymer is a homopolymer of butadiene.

12. A curable composition as defined in claim 1 12 wherein the butadienepolymer is a copolymer of acrylonitrile and butadiene.

13. A curable composition as defined in claim 1 wherein the butadienepolymer has a molecular weight of about 500 to about 15,000.

14. A curable composition as defined in claim 1 wherein the butadienepolymer has a molecular weight of about 1,000 to about 10,000.

15. The cured product of the composition defined in claim 1. Y

16. A composition as defined in claim 1 comprising3,4-epoxycyclohexylnrethyl 3,4 -epoxycyclohexane carboxylate, ahomopolymer of butadiene and hexahydrophthalic acid anhydride.

17. A composition as defined in claim 1 comprising3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate, a copolymerof butadiene and acrylonitrile and hexahydrophthalic acid anhydride.

18. A curable composition as defined in claim 7 wherein the phenolichardener is a phenol-formaL dehyde novolac resin.

19. A curable composition as defined in claim 8 wherein the polybasicacid is phthalic acid.

UNITED STATES PATENT OFFICE CERTIFICATE OF CQRRWYHON Patent No. 3 ,686,359 Dated August 22 1972 Inventor(s) Anthony C. Soldatos and Allison S.Burhans It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Column 10, lines 52-60 the formula should read as follows:

R R R3 R2 H O-ER -ocH a i 0 R5 R5 5 i O R9 Signed and sealed. this 9thday of January 1973..

(S EAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents ORM 5 0-1050 (10459) USCOMM-nr' awn:

2. A curable composition as defined in claim 1 wherein thecycloaliphatic epoxide is a cyclohexane diepoxide.
 3. A curablecomposition as defined in claim 1 wherein the cycloaliphatic epoxide hasthe formula:
 4. A curable composition as defined in claim 3 wherein R1through R9 are hydrogen and R is (CH2)4.
 5. A curable composition asdefined in claim 1 wherein the cycloaliphatic epoxide has the formula:6. A curable composition as defined in claim 5 wherein R1 through R9 arehydrogen.
 7. A curable composition as defined in claim 1 wherein thehardener is a phenolic epoxy hardener having at least two phenolichydroxyl groups per molecule.
 8. A curable composition as defined inclaim 1 wherein the hardener is a polybasic acid having at least twocarboxylic acid groups per molecule.
 9. A curable composition as definedin claim 1 wherein the hardener is an anhydride of a polybasic acid. 10.A curable composition as defined in claim 9 wherein the anhydride ishexahydrophthalic acid anhydride.
 11. A curable composition as definedin claim 1 wherein the butadiene polymer is a homopolymer of butadiene.12. A curable composition as defined in claim 1 wherein the butadienepolymer is a copolymer of acrylonitrile and butadiene.
 13. A curablecomposition as defined in claim 1 wherein the butadiene polymer has amolecular weight of about 500 to about 15,000.
 14. A curable compositionas defined in claim 1 wherein the butadiene polymer has a molecularweight of about 1,000 to about 10,000.
 15. The cured product of thecomposition defined in claim
 1. 16. A composition as defined in claim 1comprising 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexane carboxylate, ahomopolymer of butadiene and hexahydrophthalic acid anhydride.
 17. Acomposition as defined in claim 1 comprising 3,4-epoxycyclohexylmethyl3,4-epoxycyclohexane carboxylate, a copolymer of butadiene andacrylonitrile and hexahydrophthalic acid anhydride.
 18. A curablecomposition as defined in claim 7 wherein the phenolic hardener is aphenol-formaldehyde novolac resin.
 19. A curable composition as definedin claim 8 wherein the polybasic acid is phthalic acid.